Since time immemorial mothers have been lulled their babies to sleep and nothing seems more natural than to have a cradle or a baby bed which is rocked rhythmically to induce sleep.
However, it has been only recently that the medical profession has understood the problem of apnea, particularly in premature infants.
It has been found important to stimulate infants, especially premature babies with gentle, non-cyclic vibrations to prevent apnea, and also to help keep the respiratory airways clear of secretions.
Recent inventors have developed a great variety of inflatable air mattresses which operate in a progressive manner, so as to provide an undulating or massaging effect. Particularly noteworthy of this prior art is the device shown in Glass U.S. Pat. No. 3,467,081 which is intended to provide a massaging or soothing action similar to the beating of a mother's heart.
A further illustration of this prior art approach is the device shown in Cummins U.S. Pat. No. 4,066,072.
Needless to say, the use of an air-inflatable mattress for many purposes, including medical support, is old in the art, and attention is drawn to Jones U.S. Pat. Nos. 3,390,675; Murray 3,446203; Emerson 3,477,071 and Randall 4,068,334.
The method and apparatus for providing a rhythmic oscillatory support for a body on an air mattress is shown in many of the foregoing patents, but especially in Gorran U.S. Pat. No. 4,135,500.
As has been stated, the purpose of the prior art has been primarily to provide a mattress filled with air for generally comfortable support, or if an oscillatory action is desired, it has apparently always been directed toward a rhythmic and regular periodic vibration.
In one prior art patent, Thomas U.S. Pat. No. 3,587,568, the inventor had in mind precisely the goal of the present invention, namely, to inflate or deflate a mattress in out-of-phase relationship.
However, though the goal may be the same, the apparatus and method described by Thomas is a very complicated (and probably expensive) valve-arrangement to control the vibratory action.